A, Ethernet, due to its ease of deployment, continuously increasing bandwidth, declining cost and standardization efforts by Metro Ethernet Forum is fast replacing layer 2 transport technologies like Frame relay, Asynchronous Transfer Mode (ATM) and T1/E1. To be a true carrier class service, Ethernet was required to be scalable enough and have mechanisms to control connections.
IEEE 802.1Q, the standard promulgated by IEEE 802.1 workgroup for the sharing of the physical Ethernet network link by multiple independent logical channels, supported only 4096 virtual local area networks (VLANs), and with the growth of networks and the need to bridge and manage local area networks (LANs) through metropolitan area network (MAN) or other backbone networks, this limitation started to become more acute. To improve Ethernet's scalability and manageability, IEEE introduced IEEE 802.1QinQ (commonly known as stacked VLAN) which extends the Virtual LAN tagging mechanism by tagging the tagged packet thereby producing a “double-tagged” packet (i.e. frame).
For example, in a stacked VLAN arrangement, IEEE 802.1Q VLAN tags are encapsulated within a second layer of 802.1Q tag on provider-edge (PE) routers. Thereby expanding the available VLAN space from 2^12 (VLAN id is a 12 bit field in 802.1Q frame) to 2^24. Also, this allows service providers to use a single VLAN (referred as PE-VLAN or service VLAN) to support customers who have multiple VLANs (referred as CE-CLAN or customer VLAN). The core service-provider network carries traffic with double-tagged, stacked VLAN (802.1Q-in-Q) headers of multiple customers while maintaining the customer VLAN identifier and Layer 2 protocol configurations of each customer and keeping traffic in different customer VLANs segregated.
The 802.1Q tag is 4 bytes long, such that the Q-in-Q packet therefore has two 4 bytes long 802.1Q tags. These tags are generally inserted between source MAC address (SA) and Ethertype field of an untagged packet. The first two bytes of the tag are reserved for a tag protocol identifier. Of the next two bytes, first 3 bits are used to indicate the packet priority (priority code point), 4th bit is used as canonical format indicator and the remaining 12 bits specify the VLAN to which the framer belongs.
Normal Ethernet packets have a maximum payload size of 1500 bytes. With QinQ tags, packet header and other overhead the efficiency can be calculated as payload size divided by packet size (1500/1546), or 97.024%. Unfortunately, the protocols described above exhibit various limitations, such as redundancy, increased data packet size by virtue of the double-tagged” packet, etc. There is thus a need for addressing these and/or other issues associated with the prior art.